State and Fault Estimation For Infinitely Unobservable Descriptor Systems Using Sliding Mode Observers

This paper presents a novel scheme for estimating states and faults for a class of in nitely unobservable descriptor systems using sliding mode observers (SMOs). Treating certain states of the original in nitely unobservable system as unknown inputs results in a reduced-order system that is in nitely observable. Then by designing the SMO based on the reduced-order system, state estimation and fault reconstruction is achieved, thus relaxing the in nite observability requirement of the original system. The necessary and suf cient conditions in terms of the original system matrices are also investigated. A simulation example verifies the claims made in this paper.